The present invention relates generally to communications systems and, more particularly, to a method and apparatus for data communications over pressurized gas. Specifically, the invention relates to a transceiver or transmitter and receiver configured to communicate data over a gas supply line to control a remote device.
There are a variety of welding-type processes that require both power cables and gas lines. An example of where such a system would be particularly useful is in welding systems where power and gas supplies are remote from the welding location. Specifically, Tungsten Inert Gas (TIG) welding systems include a tungsten electrode to generate a welding arc and an inert shielding gas to protect and improve the weld. Additionally, Metal Inert Gas (MIG) welding, formerly known as Gas Metal Arc Welding (GMAW), combines the inert shielding gas of TIG welding processes with a continuous, consumable wire electrode.
These welding systems are useful in welding a variety of metals and alloys, for example, steel, aluminum, and stainless steel. Therefore, welding systems have been utilized in a wide variety of applications from remote field pipe line construction and repair projects to industrial shipbuilding applications. In many of these applications, the welding location is often well removed from the stationary position of both the shielding gas supply and the power source. Accordingly, welding systems have been developed that include a portable welding torch and/or a portable wire feeder system that is transportable to a welding location. These portable torches and wire feeders can be moved to a location desirable for performing the welding process while the large, bulky, and heavy power source and shielding gas supply remain fixed at a remote location. Accordingly, shielding gas and power must be delivered from the remote power source and shielding gas supply to the portable wire feeder and welding torch.
While these welding systems allow improved mobility so that an operator can move about more freely, these systems typically do not allow the operator to manipulate the operational parameters of the welding system from the welding location without the addition of a control cable specifically dedicated to such a purpose. Therefore, before traveling to the welding location, an operator inputs an initial set of operational parameters to the power source through a user interface located on the power source. However, once the operator has reached the remote welding location, the operator may need to augment the operational parameters. In this case, the operator must either return to the power source to make the necessary adjustments or communicate the requested modifications to an assistant. If the operator is working alone, the operator must travel from the welding location back to the remote power source, input the augmented operational parameters into the power source, and then travel back to the welding location. On the other hand, should the operator have an assistant, operator travel to and from the power source may be alleviated but include the added cost of additional personnel and the consumption of additional man hours. As such, assistants are not typically utilized and instead of traveling to and from the power source, in practice, the adjustment is often not made. Instead, the operator elects to force the welding process to conform to the present parameters rather than the desired parameters. This can result in less than optimal weld quality.
To alleviate the need to repeatedly travel to and from the welding location and power source or communicate to an assistant, some welding systems have included a remote control to communicate over a cable running between the remote control and the power source. In this case, augmented operational parameters may be input into the remote control and then communicated across a communications link back to the remote power source. Such a link would preferably be incorporated into the cables carrying welding power so that the operator need only pull one cable and a gas supply line to the remote location. While these remote control systems allow the operator to communicate changes in operational parameters remotely, a significant drawback to these cable-based remote controls is that the control cable is relatively fragile. As such, since welding machines are commonly used at construction sites, such as shipyards, where it is not uncommon for the cables and lines to be periodically relocated or surrounded by heavy equipment operating in the same area, such communications cables are readily prone to damage. These remote control communications cables can become damaged by being crushed or snagged by surrounding machines and/or traffic. Furthermore, should the communications cable become damaged, this may, in turn, cause damage to the wire feeder and/or the welding power source if internal power conductors come in contact with sensitive circuitry via a short to the internal communication cables.
As such, many welding systems have been developed to allow remote communication of changes to the operational parameters without introducing an additional communications link between the remote control and the power source. For example, some remote controlled systems include a radio-frequency (RF) transmitter remote control. This approach has several disadvantages. First, electric arc welding may create RF interference that negatively affects the communication between the remote transmitter and the receiver at the power source. Second, if the system is used inside metal structures such as tanks, ships, or large aircraft, the radio link can be lost due to the shielding effect of the metallic surroundings. Third, if multiple welding stations use a radio link for remote control, each remote control system, both transmitting and receiving ends, typically requires a unique identifier to prevent cross-talk or mis-transmission of control signals between the welding machines. That is, since the transmitter and receiver nodes are not connected by a wire, the possibility exists that a transmitter and receiver from two different machines may inadvertently communicate. In this case, the welding systems may operate incorrectly due to this cross-talk or miss-transmission of control signals.
Alternatively, some remote control systems have been integrated with wire feeders such that the remote control can communicate with the power source via the positive and negative electrode of the welding power cable. In this case, the welding power cable serves the dual purpose of supplying welding power to effectuate the desired welding process as well as functioning as the communications link to allow the integrated remote control of the wire feeder to communicate with the remote power source. Additionally, systems that employ high-frequency (HF) starting may induce noise within the welding power cable that can interfere with any communications traveling along the welding power cable.
Therefore, it would be desirable to design a communications system that is capable of accurately controlling a remotely located welding power source without introducing additional communications conduits or components that significantly affect the portability of the wirefeeder or welding torch of the welding system. Additionally, it would be desirable to design a welding system that is virtually impervious to RF or other electrical interference.